Security devices for allowing restricted partial opening of a door but preventing full access through the door are used widely to enable the elderly, infirm or otherwise physically vulnerable to speak to visitors or receive deliveries at their doorstep without having to admit the visitor into their home.
The most common form of such security devices comprises a chain permanently attached to the jamb of a doorway, the free end of which may be selectively engaged with a socket fixed to the inside of the door so that the door may be restrained from opening beyond the limited distance allowed by the chain. Such devices are, however, far from ideal since they are susceptible to breakage by the determined intruder and can even be disengaged from the socket on the inside of the door in cases where the intruder is able to reach around the door opening.
More robust and substantial door guards have been developed comprising props or braces to brace the door against inward opening. These are not only far less susceptible to breakage by enforced entry, but are also far less accessible to tampering with from outside the door.
Examples of prior door braces or props are disclosed in U.S. Pat. No. 4,079,972; U.S. Pat. No. 4,070,049; PCT WO 89/03469; GB 2 186 909 A; GB 2 173 543 A; and GB 2 094 882 A.
In all of these security devices the brace or prop is a tube or bar, generally of metal and hollow, that extends from an anchorage on a wall or other fixed surface behind the door to a mounting attachment on the rear, i.e. inner, face of the door. In many of these cases the prop or brace is designed to be permanently or semipermanently attached to the rear face of the door and to selectively flex or telescope to disable the bracing action when it is not required.
These existing designs of prop-type door security devices increasingly have too many moving parts and fail to optimise performance characteristics with cost and ease of assembly. Furthermore, little consideration has been given in the prior art designs to the need for external disablement of the prop in case of emergency or by trusted visitors when the home occupant is unable to come to the door. Elderly home owners, for example, may have great difficulty in answering the door to visitors and yet may receive frequent visits by trusted individuals such as friends, relatives or care workers. It is important, therefore, that the home owner can give the trusted visitors means of externally disabling the door security device.